“Lizards are becoming extinct in many places, and scientists who have studied them say it is because of rising temperatures. The heat affects reproduction. The results were clear. These lizards need to bask in the sun to warm up, but if it gets too hot they have to retreat into the shade, and then they can't hunt for food,” said Barry Sinervo of the Department of Ecology and Evolutionary Biology at the University of California, Santa Cruz.

He said he was “stunned and saddened” by the finding, reported in Friday's edition of the journal Science.

“This is an extinction alert for all areas of the globe and for all the various species of lizards,” Sinervo said.

In Mexico's Yucatan region, scientists found that the time lizards could be out foraging had disappeared. “They would barely have been able to emerge to bask before having to retreat,” Sinervo said.

Jack Sites, a biology professor at Brigham Young University, said high temperatures during the reproductive cycle prevent the animals from eating enough to to support a clutch of eggs or embryos. “The heat doesn't kill them. They just don't reproduce,” he said. “It doesn't take too much of that and the population starts to crash.”

In Madagascar, the estimate is that one-fifth of all the local lizard populations are now extinct, Sinervo said.

“This will surely have driven some endemic species to the brink of extinction, if not over the precipice,” he said in an interview via e-mail. — AP

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